Flea Control

What have y'all found to be the most effective predators of fleas? They get gnarly around these parts.  

What animal are you trying to protect?  Because fleas live on larger, warm-blooded hosts, the only effective predators would be some creature that the host is disposed to tolerate, like the birds you see on African rhinos in nature documentaries.  I don't know of any predators playing that role for dogs and cats.  Most flea treatments are based on killing the fleas through chemical or environmental means, like diatomaceous earth dehydrating the fleas and other invertebrates.

I fought fleas here in central Texas for years with no success. I didn't want to use harsh chemicals both for the dog's sake and the creatures in my yard. I used DE on the dogs and mixed it in with their food but I could never get rid of them.
I didn't know what to do until I learned, and I am not sure where I learned it from, that a mix of DE, salt, and sulphur spread on the yard would kill the fleas and keep snakes away. It worked. The rain dissolved the mix two years ago and the next year, last summer, we had no fleas. None. Even though the neighbors still had them. We still have bugs of all types but the fleas are gone. We have never had any problem with ticks, which is great, and the scorpions are a rare sight.

I don't think you will get anywhere with the natural approach to fleas. Especially if they're already causing trouble. Sorry to be negative about the attempt.
I use Frontline on the cats (be advised that in some places in the US, the fleas are resistant to it) and Trifexis on the dogs.

This is the best I've found so far: https://richsoil.com/diatomaceous-earth.jsp

we get fleas most summers, but following the instructions, it's very easy to stop them from moving into our home.